... I guess I can't use the existing options in the control library called "ChildrenComboBox" as the property isn't an object...
I believe you're right. I've looked at the code for
ChildrenComboBox (and the virtually identical
SiblingsComboBox) and it appears to be designed for handling A/V objects. I don't recall seeing this UI control used for anything other than selecting A/V inputs.
Of course, that doesn't mean one cannot define a new flavour of ComboBox (or any other type of UI control). But it does mean adding a new class to the
ControlPanelManager (a sub-module of
AutomationBrowser). I'm exploring this avenue and, if successful, I'll post the code for a
MultiValueComboBox class.
Feel free to give it a shot yourself but be aware that you'll be in
terra incognita; there's very little information to be found on the subject of enhancing the AutomationBrowser.
ADDENDUM
OK, I got it working. MultiValueComboBox displays the current value of a Multivalue property and allows you to select from all values of the associated Enumeration. I'll post it as a Module in the Downloads section.